You could probably get away with using an 8 1/4 for a while but definately upgrade to an 8 3/4 or 9 1/4.
If your set on a 440 and you have a good one I definatly would use it that low rpm torque you get out of big cubic inches is tuff to beat.
I have a 77 Ramcharger that I have a very mild 500 cubed big block with 3.23 gears and its a total blast to drive around town, no loose sloppy convertor and idles great sitting in traffic.